Means for synchronizing hydraulic rams



Patented May 27, 1941 MEANS FOR sYNonRo RAMS NIZING HYDRAULIC Kenneth 0. Monroe, Hudson, Mass., assignor' to The La Pointe Machine Tool Company, Hudson, Mass, a corporation of Maine Application June 20, 1938, Serial No. 214,755

5 Claims. (01. 60-52) This invention relates to duplex hydraulic machine tools, such as duplex broaching machines, and relates particularly to machines in which hydraulic rams move vertically in the machines and move simultaneously in opposite directions.

In the operation of such machines, it is customary to force oil back and forth between the lower ends of the ram cylinders during the alternate movements of the rams in opposite directions, and it is necessary that a full supply of oil be present in these cross-connected cylinders in order to obtain satisfactory and efllcient'operatioii. Otherwise, one ram may complete its downward or working stroke before the other ram has been fully raised and this failure to completely raise the idle ram may prevent removal and replacementof the work or may produce other undesirable results.

It is the object of my invention to provide improved means for automatically maintaining a full supply of oil in the cross-connected portions 01' a duplex hydraulic machine, and for promptly replacing any oil which may be lost in operation or while the machine stands idle.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawing which is a diagrammatic view, partly in section, of duplex hydraulic mechanism embodying my improvements.

Referring to the drawing, I have shown portions of a duplex broaching machine, including slides i and II connected to rams or pistons l2 and I3 slidable in cylinders and [5. A pump P is connected by pipes 20 and 2| to the upper ends of the cylinders i4 and I5 respectively, and the lower ends of the cylinders are cross connected through a pipe 22, back-pressure valve 23, pipe 24, relief valve 25, pipe 26, back-pressure valve 21 and pipe 28. v

The pump P is preferably of the variable discharge reversible type, such as is shown for instance in West Patent No. 1,722,832, and the direction and rate of discharge is controlled by a lever 30 pivoted at 3| and connected by a link 32 to a rack bar 33 which engages a pinion 34 in the pump P-. a I

By moving the lever 30 and rack bar 33 in either direction from the neutral position shown in the drawing, the pump P may be caused to discharge at any desired rate into the pipe or into the pipe 2|, as selected. The lever may be operated manually or by any suitable automatic devices.

An auxiliary pump P is also provided, which is connected through a pipe 40, relief valve 4| and pipe 42 to supply oil under pressure for operating fixtures, shifting valves and efiecting other desired results, the pump P being continuously operated at constant speed and the excess oil being returned to storage from the relief valve 4| through a pipe 43.

The parts thus far described are or may be of the usual type and construction and in themselves form no part of my present invention.

In the machine shown, it is customary to stop the machine with the right-hand slide II and ram H! in lowered position, and the left-hand slide in and ram l2 in raised position. These rams and slides in modern broaching machines have attained large size and extremely heavy weight, and it is found that, it such a machine is left idle for a considerable period, the raised slide and ram will drift downward by slow leak age of oil past the piston I2 or by reason of temperature changes. Such lowered position of the ram I0 is indicated in full lines in the drawing, while the fully raised and desired position is indicated in broken lines.

I will now describe my improved construction by which the raised slide andram are maintained in normal position or are quickly restored thereto. valve 4] through a branch pipe 50, valve 5|, pipe 52; valve 53, pipe 54 and check valve 55 to the pipe '22, previously described, which connects I into the lower end of the cylinder ll.

The valve 5| is spring operated and is open only when a cam plate on the slide ll engages the valve plunger 6|. Such engagement takes place only when the slide II is in its extreme lowered position.

The valve 53 is also spring operated but is normally open except when closed by engagement of a cam plate 62 on the slide to with the plunger 63 of the valve, which engagement takes place only when the slide [0 is in fully raised position. a

I also provide a by-pass 10 from the pipe 20 to storage through a valve II. This valve II is spring-operated and is controlled by a cam 12 engaging the valve plunger 13 and attached to and movable with the lever 30. These parts are so positioned that the valve H is open when the lever 30 is in neutral or mid-position, but is positively closed if the lever 30 and cam 12 are moved in either direction from mid-position.

For this purpose I connect the relief Having described the details of construction of my improved synchronizing means, I will now describe the operation thereof.

Assuming that the machine has been idle for some time and that the slide l and ram l2 have drifted downward to the position shown in full lines in the drawing, the operator in starting up the machine will first start the motors for the pumps P and P. The pump P, being in neutral position, will deliver no oil and will produce no effect, but the pump P will deliver oil under pressure to the relief valve 4| and pipes 42 and 50.

As the slide II is in its lowered position, the valve 5| will be open, and as the slide I0 is not in extreme raised position, the valve 53 will be open. Consequently, oil under pressure from the pump P will'be delivered through the check valve 55 and pipe 22 into the lower end of the cylinder H and will force the ram I2 and slide l0 upward until the slide l0 reaches its fully raised position and closes the valve 53.

The parts are thus placed in normal position for satisfactory operation, and this same action will take place at any time during the operation of the machine if the slide I0 fails to move to its fully raised position.

The check. valve 55 prevents escape of oil from the cross connection between the cylinders H and I5 during normal operation of the machine, and the back-pressure valve 23 prevents escape of oil through the cross connection to the cylinder l5 during the restoration of the ram l2 and slide III to fully raised position, the relief valve 4| being set for lower pressure than the backpressure valve 23.

It will be obvious that the oil which has leaked past and above the piston l2 must be ejected from the cylinder H as the piston I2 is raised, but this oil cannot be forced into or through the pump P when the latter is in neutral position. The bypass becomes operative under these conditions, and the excess oil in the upper part of the cylinder I4 is forced out to storage through the pipe 10 and valve H, which valve is then open, as the lever 30 is in mid-position andthe pump P is in neutral.

As soon, however, as the pump P is rendered operative by shifting the lever 30 in either direction, the valve H closes, so that no oil can escape through the by-pass 10 while the machine is in operation.

One great advantage of the described stabilizing means is that it requires no attention from the operator but becomes automatically effective to restore the parts to normal operating relation as soon as the pump P" is started. The stabilizing means also acts without attention or supervision to restore the normal relation of the rams and slides during the operation of the machine, if such normal relation is disturbed for any cause such as leakage or change in temperature. One outstanding advantage of my improved stabilizing means is its extreme simplicity. No adjustments of any kind are required and the invention works equally well, whether the machine is operated idle or under load.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. In a duplex hydraulic machine tool having two main cylinders cross-connected together at one end of each, a pump selectively operable to supply oil under pressure to the other end of one or th other of said cylinders, and slides connected to pistons in said cylinders and thereby movable simultaneously but oppositely vertically, that improvement which consists in providing an additional supply of oil under constant pressure, a passage to admit said oil to the crossconnected end of a first cylinder, a first valve in said passage which is open unless the piston and slide associated with said first cylinder is in extreme raised position, a second valve in said passage in series with said first valve and which second valve is closed unless the piston and slide associated with the second cylinder are in extreme lowered position, and a relief valve in the cross-connection which is set to open only at a pressure in excess of the constant pressure in said passage.

2. The combination in a machine tool as set forth in'claim 1, in which a reversible discharge pump provides the oil to actuate said pistons and slides, and in which a discharge valve is provided for escape to atmosphere of surplus oil above th piston in said first cylinder when said piston is below its fully raised position at the time the piston in the second cylinder is in its fully lowered position, but said discharge valve being open only when said pump is in no-discharge position and being automatically closed whenever said pump is supplying oil to either main cylinder.

3. The combination in a machine tool as set forth in claim 1 in which said first valve is closed and said second valve is opened by devices on the slides when moved to their extreme raised and extreme lowered positions, respectively.

4. In a duplex hydraulic machine tool having two main cylinders cross-connected together at one end of each, a pump selectively operable to supply oil under pressure to the other end of one or the other of said cylinders, and slides connected to pistons in said cylinders and thereby movable simultaneously but oppositely vertically, in combination, separate means to supply makeup oil under constant pressure to one of said cross-connected cylinders, automatic means to prevent such make-up oil entering said cylinder unless the piston in said cylinder is below its upper limit of travel and the piston in the other cylinder is at its lower limit of travel, and a relief valve in the cross-connection which is set to open only at a pressure in xcess of the pressure of said make-up oil.

5. In a duplex hydraulic machine tool having two main cylinders cross-connected together at one end of each, a pump selectively operable to supply oil under pressure to the other end of one or the other of said cylinders, and slides connected to pistons in said cylinders and thereby movable simultaneously but oppositely vertically, in combination, separate means to supply makeup oil under constant pressure to one of said cross-connected cylinders when the piston in said cylinder is below its upper limit of travel and the piston in the other cylinder is at its lower limit of travel, a device to freely vent said one of said cross-connected cylinders at the end opposite to which said separate means is supplying make-up oil when said pump is in no-discharge position and a relief valve in the crossconnection which is set to open only at a pressure in excess of the pressure of said make-up oil.

KENNETH C. MONROE. 

